Applicator devices for endoprostheses are known which include a sheath in which the future prosthesis is placed in the radially contracted state, prior to its implantation. A support rod passes through the sheath, inside this same prosthesis. To make them easier to trace, some applicators include beads or rings of radiopaque material, in particular of gold or platinum (as described e.g. in U.S. Pat. No. 5,201,901) or tantalium (U.S. Pat. No. 5,480,423), which are fitted on the support rod, at the distal and proximal ends of the prosthesis in its radially contracted shape. Metallic markers may also be fitted on the outer sheath, as in U.S. Pat. No. 5,026,377. The disadvantage of these markers lies in their relative axial and radial bulk, in their price and in the fact that the operator has to fully perfect the procedure for deployment of the endoprosthesis, whose length, when contracted, can be very considerable (up to 300%) compared to its length when deployed. In addition, the variation in length is also a function of the type and the diameter of the endoprosthesis.